Method of manufacturing inner tubes



March 27, 1934. w STEPHENS 1,952,470

METHOD OF MANUFACTURING INNER TUBES Filed Aug. 12, 1931 gwuento'v damn45 various strips into a single, composite tube or Patented Mar. 27,1934 UNITED STATES 1,952,470 METHOD OF MANUFACTURING INNER TUB WilliamStephens, Akron,

Ohio, assignor, by

mesne assignments, to Wingfoot Corporation, Wilmington, Del., acorporation of Delaware Application August 12, 1931, Serial No. 556,578

2 Claims.

The invention relates to the manufacture of composite bodies of plasticmaterial, and more particularly to the manufacture of rubber inner tubesand like rubber bodies which are built up of portions of differentrubber compounds.

One object of the invention is to provide a method ofymaking an innertube for pneumatic tires which produces a body having portions ofdistinct compositions, which portions are particularly adapted forservice and long wear in the position they assume in the tire and wheelassembly.

Another object of the invention resides in the provision of a methodofrrapidly, inexpensively and efficiently producing composite plasticbodies of the class described.

Another object of the invention is to provide a method for producingfiat bodies of composite materials.

According to the present invention, rubber inner tubes are producedhaving an inner peripheral portion of a rubber compound which is ofabrasive resisting nature, and an outer peripheral portion of a compoundof high heat-resisting nature. In this manner the inner periphery of thetube can be of such compound that the tube can be used with drop centerrims or with rims without tire flaps, or under other similar condiofcylinders for the extrusion of rubber compounds, each cylinder beingdesigned to extrude a particular type of stock and then passing thematerials emerging from these cylinders through a common die which isdesigned to unite the body.

The invention also contemplates employing the method herein described tomake fiat composite bodies, and in this respect it is particularlyadapted to the making of a combination tread and sidewall unit or memberfor use on pneumatic tires. This is because the tread portion must be ofa tough, long wearing, comparatively expensive composition and thesidewalls may be of relatively cheaper materials, or of a compoundparticularly designed to withstand fiexure rather than wear. In thismanner the tread and sidewalls can be made of any respectivecompositions and yet be produced and handled in a single unit or pieceof material.

,For a better understanding of the invention, reference may now be hadto the accompanying drawing, forming a part of the specification, ofwhich:

'Fig. 1 is a perspective view of a cross-sectional portion of avulcanized inner tube constructed in accordance with the invention;

Fig. 2 is a cross-sectional view taken through an unvulcanized length ofinner tube formed in accordance with the invention;

Fig. 3 is an elevational view of an extruding machine employed inpracticing the invention;

Fig. 4 is a fragmentary elevational view of a die head employed intheextrusion of a tread and side-wall unit; and y 4 Fig. 5 is across-sectional view of a tread and side-wall unit as produced by thedie head of Fig. 4. Y

Referring to the drawing, the numeral 10 indicates an inner tube formedin accordance with the method embodying the invention, which tubecomprises an outer peripheral portion 12 of a rubber compound markedtread wall stock and an inner peripheral portion 14 formed of a rubbercompound marked base wall stock. The walls 12 and 14 are preferablyjoined by butt joints 16 which define circumferentially extending lines.The tread wall stock 12, that is the stock forming the portion of thetubeadjacent the tread of the tire has high heat-resistingcharacteristics, while the base wall stock forming the base or rimcontacting portion of the tube has high abrasive resisting qualities.While the portions 12 and 14 have been particularly described aspossessing certain characteristics, it will be understood that the exactcharacteristics of the respective compounds may be widely varied so thatany desired qualities may be given to the respective portions.

In manufacturing composite tubes such as the tubes 10, a multi-cylinderextruding machine of the type illustrated in Fig. 3 may conveniently beemployed. This machine may comprise a pair of aligned cylinders 18containing suitably driven extruding means of the ordinary type, thecylinders 18 being connected with a common extruding head or die 20. Thetwo materials are formed into curved sheets by suitable die passages int e head 20 and are then passed through a common circular opening wherethe edges of the sheets are united to form a tube. Co-pendingapplications, Serial Numbers 501,332 and 509,388, which are assigned tothe same assignee as the present application, illustrate apparatus ofthis type.

In constructing the tube 10, the material comprising the one portion ofthe tube will be fed to one of the extruding cylinders while thematerial comprising the other portion of the tube will be fed to theother cylinder. The extruding cylinders or machines will then feed therespective materials to the common extruding die 20, through which theywill be passed in the form of the unvulcanized tube indicated in Fig. 2.Thereafter the unvulcanized tube is cut into proper lengths and providedwith valve stems, the ends of each length are joined, and the tubes arevulcanized in unitary molds, as will be understood. The handling of thetube after the tubing operation is thus very similar to the handling ofthe ordinary inner tube built by the extrusion method.

While the method described and illustrated embodies forming a tube inwhich the portions 12 and 14 each comprise substantially equal halves ofthe tube 10, it will be seen that by changing the form of the extrudinghead 20 that the portions 12 and 14 may be unequal, i. e., the oneportion may extend a greater distance around the tube than the other.Moreover, it is not essential that the portions 12 and 14 be joined bybutt joints 16, inasmuch as these joints may take the form of skived lapjoints or the like.

Referring to the form of the invention illustrated in Fig. 5, thenumeral 22 indicates a tread and sidewall unit comprising a treadportion 24 and sidewall portions 26. The tread portion 24 is of tough,long-wearing, comparatively expensive rubber. The sidewall portions 26may be of somewhat cheaper rubber particularly adapted to resist flexingaction.

In making the tread and sidewall unit 22, as illustrated in Fig. 5, themethod followed is substantially the same as that described above inregard to making an inner tube, except that in this case the tuber heador die 20 is preferably provided with a knife 28 which is placed asshown in Fig, 5, so that as the material is extruded in the form of atube, the knife 28 will cut the sidewall material along a longitudinalmedian line so that the tube may be then flattened into the shape shownin Fig. 5.

It will be understood that the respective compositions of the sidewalland tread material may be widely varied to meet any desired operatingconditions or to provide any quality of tire desired. Moreover, therespective thicknesses of the tread portion and sidewalls are dependentonly upon the shape of the extruding head, which may be changed asdesired. It will also be apparent that the tread portion 24 and thesidewall portions 26 may extend other than half way around the extrudedtube, as explained above in regard to the inner tube, by merely changingthe passages of the respective materials to the extruding die 20.

While the invention has been particularly described in regard to makinginner tubes and tread and sidewall units, it will be evident that theprinciples thereof are broadly applicable not only to forming compositerubber bodies but also to forming composite bodies of various otherplastics.

It will also be understood that the invention contemplates not onlyforming the respective compounds of different characteristics but alsoforming the compounds of different colors so that very attractiveproducts result.

Although I have illustrated and described only the preferred embodimentof the invention, it will be apparent to those skilled in the art thatthe invention is not so limited but that various modifications may bemade therein without departing from the spirit of the invention or fromthe scope of the appended claims.

What I claim is:

1. The method of manufacturing inner tubes which comprisessimultaneously extruding a plurality of rubber compounds throughindividual passages connected to a common extruding head to form a tubehaving walls of different compounds connected with butt joints extendinglengthwise of the tube, cutting the tube into lengths, joining the endsof each length together, vulcanizing each joined length with onecompound turned to the inner periphery of the tube and the other thuspositioned at the outer periphery of the tube.

2. The method of manufacturing inner tubes which comprisessimultaneously extruding a plurality of rubber compounds throughindividual passages connected to a common extruding head to form a tubehaving walls of different compounds, cutting the tube into lengths,joining the ends of each length together, vulcanizing each joined lengthwith one compound turned to the inner periphery of the tube and theother thus positioned at the outer periphery of the tube.

WILLIAM STEPHENS.

